Powder metallurgy is a technique known for manufacturing metal components. The powder metallurgy enables high-precision, high-speed and large-volume production of metal components of complicated shapes without machining. Further, powder metallurgy also enables production of alloys of various compositions only by altering composition ratio of metal powder. Thus, it is expected that powder metallurgy is used for various fields.
In the powder metallurgy, powder of alloy component, graphite and the like are mixed to a main raw material powder in order to enhance physical properties of a sintered body (e.g. strength and processability). The mixture is compacted to form a green compact, which is subsequently sintered to form a product sintered body. At this time, in order to reduce a friction between the powders and between the powder and the mold to enhance compactibility and mold releasing performance of the powder, a molding lubricant such as zinc stearate powder, lithium stearate powder and ethylene-bis-stearamide powder is usually mixed to the above metal powder (see, for instance, Patent Literature 1).